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Java example source code file (Indexer.java)

This example Java source code file (Indexer.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

annotation, bindingscopingvisitor, bindingtype, constant, convertedconstantbinding, eager_singleton, element, exposed, indexedbinding, indexer, injector, object, override, provided_by, string

The Indexer.java Java example source code

/**
 * Copyright (C) 2014 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.inject.multibindings;

import com.google.common.base.Objects;
import com.google.inject.Binding;
import com.google.inject.Injector;
import com.google.inject.Scope;
import com.google.inject.Scopes;
import com.google.inject.TypeLiteral;
import com.google.inject.spi.BindingScopingVisitor;
import com.google.inject.spi.ConstructorBinding;
import com.google.inject.spi.ConvertedConstantBinding;
import com.google.inject.spi.DefaultBindingTargetVisitor;
import com.google.inject.spi.ExposedBinding;
import com.google.inject.spi.InstanceBinding;
import com.google.inject.spi.LinkedKeyBinding;
import com.google.inject.spi.ProviderBinding;
import com.google.inject.spi.ProviderInstanceBinding;
import com.google.inject.spi.ProviderKeyBinding;
import com.google.inject.spi.UntargettedBinding;

import java.lang.annotation.Annotation;

/**
 * Visits bindings to return a {@code IndexedBinding} that can be used to emulate the binding
 * deduplication that Guice internally performs.
 */
class Indexer extends DefaultBindingTargetVisitor<Object, Indexer.IndexedBinding>
    implements BindingScopingVisitor<Object> {
  enum BindingType {
    INSTANCE,
    PROVIDER_INSTANCE,
    PROVIDER_KEY,
    LINKED_KEY,
    UNTARGETTED,
    CONSTRUCTOR,
    CONSTANT,
    EXPOSED,
    PROVIDED_BY,
  }

  static class IndexedBinding {
    final String annotationName;
    final Element.Type annotationType;
    final TypeLiteral<?> typeLiteral;
    final Object scope;
    final BindingType type;
    final Object extraEquality;

    IndexedBinding(Binding<?> binding, BindingType type, Object scope, Object extraEquality) {
      this.scope = scope;
      this.type = type;
      this.extraEquality = extraEquality;
      this.typeLiteral = binding.getKey().getTypeLiteral();
      Element annotation = (Element) binding.getKey().getAnnotation();
      this.annotationName = annotation.setName();
      this.annotationType = annotation.type();
    }

    @Override public boolean equals(Object obj) {
      if (!(obj instanceof IndexedBinding)) {
        return false;
      }
      IndexedBinding o = (IndexedBinding) obj;
      return type == o.type
          && Objects.equal(scope, o.scope)
          && typeLiteral.equals(o.typeLiteral)
          && annotationType == o.annotationType
          && annotationName.equals(o.annotationName)
          && Objects.equal(extraEquality, o.extraEquality);
    }

    @Override public int hashCode() {
      return Objects.hashCode(type, scope, typeLiteral, annotationType, annotationName,
          extraEquality);
    }
  }

  final Injector injector;

  Indexer(Injector injector) {
    this.injector = injector;
  }

  boolean isIndexable(Binding<?> binding) {
    return binding.getKey().getAnnotation() instanceof Element;
  }

  private Object scope(Binding<?> binding) {
    return binding.acceptScopingVisitor(this);
  }

  @Override public Indexer.IndexedBinding visit(ConstructorBinding<? extends Object> binding) {
    return new Indexer.IndexedBinding(binding, BindingType.CONSTRUCTOR, scope(binding),
        binding.getConstructor());
  }

  @Override public Indexer.IndexedBinding visit(
      ConvertedConstantBinding<? extends Object> binding) {
    return new Indexer.IndexedBinding(binding, BindingType.CONSTANT, scope(binding),
        binding.getValue());
  }

  @Override public Indexer.IndexedBinding visit(ExposedBinding<? extends Object> binding) {
    return new Indexer.IndexedBinding(binding, BindingType.EXPOSED, scope(binding), binding);
  }

  @Override public Indexer.IndexedBinding visit(InstanceBinding<? extends Object> binding) {
    return new Indexer.IndexedBinding(binding, BindingType.INSTANCE, scope(binding),
        binding.getInstance());
  }

  @Override public Indexer.IndexedBinding visit(LinkedKeyBinding<? extends Object> binding) {
    return new Indexer.IndexedBinding(binding, BindingType.LINKED_KEY, scope(binding),
        binding.getLinkedKey());
  }

  @Override public Indexer.IndexedBinding visit(ProviderBinding<? extends Object> binding) {
    return new Indexer.IndexedBinding(binding, BindingType.PROVIDED_BY, scope(binding),
        injector.getBinding(binding.getProvidedKey()));
  }

  @Override public Indexer.IndexedBinding visit(ProviderInstanceBinding<? extends Object> binding) {
    return new Indexer.IndexedBinding(binding, BindingType.PROVIDER_INSTANCE, scope(binding),
        binding.getUserSuppliedProvider());
  }

  @Override public Indexer.IndexedBinding visit(ProviderKeyBinding<? extends Object> binding) {
    return new Indexer.IndexedBinding(binding, BindingType.PROVIDER_KEY, scope(binding),
        binding.getProviderKey());
  }

  @Override public Indexer.IndexedBinding visit(UntargettedBinding<? extends Object> binding) {
    return new Indexer.IndexedBinding(binding, BindingType.UNTARGETTED, scope(binding), null);
  }
  
  private static final Object EAGER_SINGLETON = new Object();
  
  @Override public Object visitEagerSingleton() {
    return EAGER_SINGLETON;
  }

  @Override public Object visitNoScoping() {
    return Scopes.NO_SCOPE;
  }

  @Override public Object visitScope(Scope scope) {
    return scope;
  }

  @Override public Object visitScopeAnnotation(Class<? extends Annotation> scopeAnnotation) {
    return scopeAnnotation;
  }
}

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